NODULES ARE INDUCED ON ALFALFA ROOTS BY AGROBACTERIUM-TUMEFACIENS AND RHIZOBIUM-TRIFOLII CONTAINING SMALL SEGMENTS OF THE RHIZOBIUM-MELILOTI NODULATION REGION
NODULES ARE INDUCED ON ALFALFA ROOTS BY AGROBACTERIUM-TUMEFACIENS AND RHIZOBIUM-TRIFOLII CONTAINING SMALL SEGMENTS OF THE RHIZOBIUM-MELILOTI NODULATION REGION
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DOI：
10.1128/jb.161.1.223-230.1985
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发表时间：
1985-01-01
影响因子：
3.2
通讯作者：
LONG, SR
中科院分区：
文献类型：
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作者：
HIRSCH, AM;DRAKE, D;LONG, SR
通过接合将来自共生质粒的苜蓿根瘤菌结瘤基因的区域转移至根癌农杆菌和三叶根瘤菌。 A. tumefaciens 和 R. trifolii 转接合子不能引起苜蓿根毛卷曲，但能够以低频率诱导根瘤发育。根据细胞学和发育标准，这些被判断为真正的结节。与真正的苜蓿根瘤一样，这些根瘤是由内根皮层细胞的分裂起始的。它们发育出位于远端的分生组织和几个外周维管束。内皮层将结节的内部组织与周围的皮质分开。没有发现感染线穿透根毛或根瘤细胞。仅在细胞间隙中发现细菌。因此，由携带苜蓿根瘤菌小结瘤克隆的根癌农杆菌和三叶根瘤菌转接合子诱导的苜蓿根瘤完全没有细胞内细菌。当这些菌株接种到白三叶草根上时，会出现小的结节状突起，当进行细胞学检查时，发现它更类似于根而不是结节。尽管分生组织变宽并且没有根冠，但突出物具有中央维管束和其他根状特征。我们的结果表明，苜蓿根瘤的形态发生可以与感染丝的形成脱钩。 8.7-kilobase 结瘤片段中编码的基因足以在根癌农杆菌或三叶根瘤菌背景中进行根瘤形态发生。
Regions of the Rhizobium meliloti nodulation genes from the symbiotic plasmid were transferred to Agrobacterium tumefaciens and Rhizobium trifolii by conjugation. The A. tumefaciens and R. trifolii transconjugants were unable to elicit curling of alfalfa root hairs, but were able to induce nodule development at a low frequency. These were judged to be genuine nodules on the basis of cytological and developmental criteria. Like genuine alfalfa nodules, the nodules were initiated from divisions of the inner root cortical cells. They developed a distally positioned meristem and several peripheral vascular bundles. An endodermis separated the inner tissues of the nodule from the surrounding cortex. No infection threads were found to penetrate either root hairs or the nodule cells. Bacteria were found only in intercellular spaces. Thus, alfalfa nodules induced by A. tumefaciens and R. trifolii transconjugants carrying small nodulation clones of R. meliloti were completely devoid of intracellular bacteria. When these strains were inoculated onto white clover roots, small nodule-like protrusions developed that, when examined cytologically, were found to more closely resemble roots than nodules. Although the meristem was broadened and lacked a root cap, the protrusions had a central vascular bundle and other rootlike features. Our results suggest that morphogenesis of alfalfa root nodules can be uncoupled from infection thread formation. The genes encoded in the 8.7-kilobase nodulation fragment are sufficient in A. tumefaciens or R. trifolii backgrounds for nodule morphogenesis.